Quantitative Separation of Copper by Thiourea from Homogeneous Solution

Quantitative separation of copper as sulfide was made from homogeneous solution containing thiourea, together with urea and ammonium chloride. It was found, that with boiling, the solution adjusted to a pH 4.0 in forty minutes or more after the first appearance of black turbidity; the precipitate is obtained in an easily filterable and washable form. Addition of ammonium chloride was found very effective in the presence of some cations. The amount of 10 to 100 mg. of copper could be satisfactorily separated from calcium and magnesium, and the separabilities from nickel, cobalt, zinc, and manganese were examined in the presence of ammonium chloride, and their allowable amount of coexistence in quantitative separation was determined.